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The CT 600 template is the company tax return itself. Silverfin fills it in from the rest of the UK Corporation Tax workflow, and that includes the supplementary pages: the extra HMRC forms (CT600A, CT600B and so on) that only some companies need. This article explains which pages Silverfin supports, what makes each one appear, where its figures come from, and how to check them before you file.

Table of contents 

• When should I use this article?
• How is the return put together?
• Which supplementary pages does Silverfin support?
• Why does starring affect some pages but not others?
• How do I check which pages are included?
• Where does the data on each page come from?
• What rolls forward next year?
• Frequently asked questions

When should I use this article?

Read it when you need a supplementary page on the return (for example a CT600A for a director's overdrawn loan account), or when a page you expected is missing or one you didn't expect is showing.

How is the return put together?

You don't add a supplementary page yourself. Silverfin includes it automatically when the template behind it has the relevant entries.

• The CT600 is built from the workflow. The CT 600 template can't be edited. Every box comes from the templates you complete earlier in the workflow, so you correct a figure by changing the template it comes from.
• Supplementary pages are switched on automatically.Each supported page has one source template. When that template holds the entries described below, Silverfin:
  • puts an X in the matching box under Supplementary pages enclosed on page 2 of the CT600, and
  • adds the full supplementary page after the declaration at the end of the CT 600 template.
• HMRC receives what you see. When you submit to HMRC, Silverfin builds the return from the same entries, so the box ticks and supplementary pages shown in the CT 600 template are the ones that are filed.
• Long periods of account. Each accounting period has its own return. The CT 600 period 2 template carries its own supplementary pages, based on the second-period entries in each source template.

Which supplementary pages does Silverfin support?

Silverfin doesn't currently produce the other supplementary pages:

• CT600D (insurance)
• CT600E (charities and CASCs)
• CT600F (tonnage tax)
• CT600G (Northern Ireland)
• CT600I (ring fence trades)
• CT600K (restitution tax)
• CT600M (freeports and investment zones)
• CT600N (residential property developer tax)
• CT600P (creative industries)

Their boxes on the CT600 are always left blank.

Why does starring affect some pages but not others?

Starring affects the pages in different ways, so it's worth knowing which is which:

• CT600A and CT600C are only included while Loans to participators or Group relief is starred. These templates are often unstarred in a new file, so star them when they apply.
• CT600B, CT600H, CT600J and CT600L follow the entries in Return disclosure or Research and development claim, whether or not the template is starred. Unstarring these templates won't remove the page.

To leave a page off the return, clear the entries that trigger it rather than unstarring the template. This keeps the CT600 consistent. For example, unstarring Loans to participators while a loan is still entered removes the CT600A, but the s455 tax can still flow to box 480 of the CT600.

How do I check which pages are included?

1. Open the CT 600 template (or CT 600 period 2 for the second accounting period of a long period of account).
2. On page 2, look at Supplementary pages enclosed (boxes 95 to 144). Each page being included has an X.
3. Scroll past the declaration. Each included page follows, headed Company Tax Return - supplementary page. Check its figures against the source template.

Where does the data on each page come from?

• CT600A: the participator names, loans, repayments, releases and dates, the tax chargeable (A20), relief (A45, A70) and tax payable (A80) all come from Loans to participators. The A80 figure is copied to box 480 of the CT600. Completing Part 3 (box A70) ticks box 485.
• CT600B: CFC details, the foreign permanent establishment election and the hybrid and other mismatches answers come from the CFC and hybrid sections of Return disclosure.
• CT600C: the claims and surrenders, with company names, accounting periods and tax references, come from the four parts of Group relief. Surrenders also need to agree with the Losses memorandum, and Group relief shows a warning until they do.
• CT600H: the recipient, payment and tax deducted details come from the cross-border royalties section of Return disclosure. The yes/no question at the top of that section fills box 645 on the CT600.
• CT600J: scheme reference numbers and the accounting period in which the expected advantage arises come from the tax avoidance schemes section of Return disclosure.
• CT600L: the qualifying expenditure, credit and PAYE/NICs figures come from Research and development claim. The R&D claim ticks on the main CT600 (boxes 650 and 655) come from Return information.
• Company name, tax reference and period at the top of each page come from Return information.

What rolls forward next year?

Nothing rolls forward on the CT600 itself. It's rebuilt each period from that period's templates. Balances that carry forward in the source templates feed next year's pages automatically. For example, an outstanding participator loan becomes the next year's Loan b/f in Loans to participators.

Frequently asked questions

How do I make sure the CT600A is included in my return?

1. Star Loans to participators in the workflow.
2. Enter each participator with their loan balance brought forward, net additions and any repayments, releases or write-offs.
3. Open CT 600 and check that box 95 has an X and that the CT600A page appears after the declaration.

If there is no closing balance, no net additions and no repayment in Part 2 or Part 3, there is nothing to report on the CT600A, so it isn't included. See How do I use the Loans to participators template? (UK market) for the template itself.

My CT600C isn't showing, but I've entered group relief. Why?

Check that Group relief is starred. The CT600C is only included while it is, and that template is often unstarred by default. Then check that the claim or surrender amount is above nil.

I've ticked the cross-border royalty payments question, but there's no CT600H. Why?

The tick on Has the company made cross-border royalty payments in the year? only fills box 645 on the main return. The CT600H is included once you enter at least one royalty payment row underneath.

I unstarred Return disclosure (or Research and development claim), but the page is still on the return. Why?

These pages follow the entries, not the star. Clear the CFC, mismatch, royalty or scheme entries (or the R&D expenditure) that no longer apply, and the page drops off.

Can I tick the supplementary page boxes on the CT600 myself?

No. The CT600 can't be edited. Boxes 95 to 144 are set from the source templates, so make the change there.

Why is a CT600L showing when the company isn't claiming R&D this year?

For periods starting on or after 1 April 2024, check whether Research and development claim still has qualifying expenditure entered, for example figures carried over in a copied file. For earlier periods, check the R&D claim ticks in Return information.

How do supplementary pages work for a long period of account?

Each accounting period gets its own return and pages. The source templates show separate entries for each period. CT 600 shows the pages for the first period and CT 600 period 2 shows the pages for the second.

The company needs a supplementary page that Silverfin doesn't support. What should I do?

Silverfin doesn't produce CT600D, E, F, G, I, K, M, N or P. Contact Silverfin support before filing a return that needs one of these pages.

This article relates to the CT 600 and CT 600 period 2 templates in the UK Corporation Tax workflow. It is provided as guidance and does not constitute tax advice.